Wen Wu-Qi

High Power Widely Tunable Narrow Linewidth All-Solid-State Pulsed Titanium-Doped Sapphire Laser

We report a widely tunable, narrow linewidth, pulsed Ti:sapphire laser pumped by an all-solid-state Q-switched intra-cavity frequency-doubled Nd:YAG laser. By using four dense flint glass prisms as intra-cavity dispersive elements, the output wavelength can be continuously tuned over 675–970 nm and the spectral linewidth is shortened to 0.5nm. The maximum output power of 6.65 W at 780nm is obtained under 23.4 W pump power with repetition rate of 5.5kHz; corresponding to an conversion efficiency of 28.4%. Due to the gain-switching characteristics of the Ti:sapphire laser, the output pulse duration is as short as 17.6 ns.

High efficiency continuous-wave tunable signal output of an intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

In this paper we report on a continuous-wave (CW) intracavity singly resonant optical parametric oscillator (ICSRO) based on periodically poled LiNbO3 (PPLN) pumped by a diode-end-pumped CW Nd:YVO4 laser. Considering the thermal lens effects and diffraction loss, an optical ballast lens and a near-concentric cavity are adopted for better operation. Through varying the grating period and the temperature, the tunable signal output from 1406 nm to 1513 nm is obtained. At a PPLN grating period of 29 μm and a temperature of 413 K, a maximum signal output power of 820 mW at 1500 nm is achieved when the 808 nm pump power is 10.9 W, leading to an optical-to-optical conversion efficiency of 7.51%.

Passively Q-Switched Quasi-Continuous-Wave Diode-Pumped Intracavity Optical Parametric Oscillator at 1.57 μm

We report on a passively Q-switched quasi-cw diode-pumped Nd:YAG including an intracavity optical parametric oscillator. The dynamics of this system is described by solving the coupled equations. The effect of the initial transmission of Cr4+:YAG saturable absorber on the signal wave operation is studied. Under optimum conditions, we achieve 2.3 m J energy at 1.57μm wavelength for 40 Hz repetition rate. The peak power of the pulses amounts to 0.88MW with the pulse width of 2.6ns. When the Fresnel reflection losses of the filters are taken into account, the pulse energy would be higher than 2.3 m J. To the best of our knowledge, this is the highest pulse energy and peak power for such a type of single resonant quasi-cw diode pumped Nd:YAG/Cr4+ :YAG IOPO laser.

High-Power Continuous-Wave Diode-End-Pumped Intracavity Frequency Doubled Nd:YVO4 Laser at 671 nm with a Compact Three-Element Cavity

We report a high-power high-efficient continuous-wave (cw) diode-end-pumped Nd:YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a compact three-element cavity. At incident pump power of 20.6 W, a maximum output power of 7 W at 1342 nm is obtained with a slope efficiency of 37.3%. By inserting a type-I critical phase-matched LBO crystal as intracavity frequency-doubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9 W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diode-pumped solid-state Nd:YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.

Three-Dimensional Thermal Analysis of 18-Core Photonic Crystal Fiber Lasers

The three-dimensional thermal properties of 18-core photonic crystal fiber lasers operated under natural convection are investigated. The temperature sensing technique based on a fiber Bragg grating sensor array is proposed to measure the longitudinal temperature distribution of a 1.6-m-long ytterbium-doped 18-core photonic crystal fiber. The results show that the temperature decreases from the pump end to the launch end exponentially. Moreover, the radial temperature distribution of the fiber end is investigated by using the full-vector finite-element method. The numerical results match well with the experimental data and the coating temperature reaches 422.7K, approaching the critical value of polymer cladding, when the pumping power is 40 W. Therefore the fiber end cooling is necessary to achieve power scaling. Compared with natural convection methods, the copper cooling scheme is found to be an effective method to reduce the fiber temperature.

All-Solid-State Nd:YAG Laser Operating at 1064 nm and 1319 nm under 885 nm Thermally Boosted Pumping

We report a high-efficiency Nd:YAG laser operating at 1064 nm and 1319 nm, respectively, thermally boosted pumped by an all-solid-state Q-switched Ti:sapphire laser at 885 nm. The maximum outputs of 825.4 mW and 459.4 mW, at 1064 nm and 1319 nm respectively, are obtained in a 8-mm-thick 1.1 at. % Nd:YAG crystal with 2.1 W of incident pump power at 885 nm, leading to a high slope efficiency with respect to the absorbed pump power of 68.5% and 42.0%. Comparative results obtained by the traditional pumping at 808 nm are presented, showing that the slope efficiency and the threshold with respect to the absorbed pump power at 1064 nm under the 885 nm pumping are 12.2% higher and 7.3% lower than those of 808 nm pumping. At 1319 nm, the slope efficiency and the threshold with respect to the absorbed pump power under 885 nm pumping are 9.9% higher and 3.5% lower than those of 808 nm pumping. The heat generation operating at 1064 nm and 1319 nm is reduced by 19.8% and 11.1%, respectively.

Performance of gain-switched all-solid-state quasi-continuous-wave tunable Ti:sapphire laser system

We have made a gain-switched all-solid-state quasi-continuous-wave (QCW) tunable Ti:sapphire laser system, which is pumped by a 532 nm intracavity frequency-doubled Nd:YAG laser. Based on the theory of gain-switching and the study on the influencing factors of the output pulse width, an effective method for obtaining high power and narrow pulse width output is proposed. Through deliberately designing the pump source and the resonator of the Ti:sapphire laser, when the repetition rate is 6 kHz and the length of the cavity is 220 mm, at an incident pump power of 22 W, the tunable Ti:sapphire laser from 700 to 950 nm can be achieved. It has a maximum average output power of 5.6 W at 800 nm and the pulse width of 13.2 ns, giving an optical conversion efficiency of 25.5% from the 532 nm pump laser to the Ti:sapphire laser.

An All-Solid-State Tunable Dual-Wavelength Ti:Sapphire Laser with Quasi-Continuous-Wave Outputs

A high power dual-wavelength Ti:sapphire laser system with wide turning range and high efficiency is described, which consists of two prism-dispersed resonators pumped by an all-solid-state frequency-doubled Nd:YAG laser. Tunable dual-wavelength outputs, with one wavelength range from 750 nm to 795 nm and the other from 800 nm to 850 nm, have been demonstrated. With a pump power of 23 W at 532 nm, a repetition rate of 6.5 kHz and a pulse width of 67.6 ns, the maximum dual-wavelength output power of 5.6 W at 785.3 nm and 812.1 nm, with a pulse width of 17.2 ns and a line width of 2 nm, has been achieved, leading to an optical-to-optical conversion efficiency of 24.4%.

An all-solid-state high power quasi-continuous-wave tunable dual-wavelength Ti:sapphire laser system using birefringence filter

This paper describes a tunable dual-wavelength Ti:sapphire laser system with quasi-continuous-wave and high-power outputs. In the design of the laser, it adopts a frequency-doubled Nd:YAG laser as the pumping source, and the birefringence filter as the tuning element. Tunable dual-wavelength outputs with one wavelength range from 700 nm to 756.5 nm, another from 830 nm to 900mn have been demonstrated. With a pump power of 23 W at 532 nm, a repetition rate of 7 kHz and a pulse width of 47.6 ns, an output power of 5.1 W at 744.8 nm and 860.9 nm with a pulse width of 13.2 ns and a line width of 3 nm has been obtained, it indicates an optical-to-optical conversion efficiency of 22.2%.